Arsenic - Alarm Warning!
by Sylvia Mortoza
The World Health Organization (WHO) safe limit for arsenic in drinking
water is 0.01 mg/l. In Bangladesh the maximum permissible limit is 0.05
mg/l. 48 out of the 64 districts of Bangladesh now show a level of contamination
higher then the maximum permissable limit. Cases of arsenic poisoning are
pouring in from all over the country.
The toxic effect of arsenic is dependent on its chemical form; route
of entry; age; sex; dosage and duration of exposure. The major portion
of the absorbed arsenic is excreted through the urine (about 50 per cent);
a small portion through faeces; skin; hair; and nails; and is firmly bound
to Keratin. Storage in metabolically dead tissues slowly eliminates it
from the body but when the poison is ingested at a rate higher than the
body's disposal system, the result is any form of the arsenic-related diseases.
In other words, if ingested faster than it can be excreted, arsenic accumulates
in the hair and fingernails.
In Bangladesh, each of the four recognized stages of arsenicosis, or
chronic arsenic poisoning, have been reached. The first two stages are
before the condition becomes irreversable so it is important to catch them
- Preclinical: the patient shows no symptoms, but arsenic can be detected
in urine or body tissue samples.
- Clinical: Arsenic-poisoning may begin with the irritation of gastro-intestinal
and upper respiratory tracts. Various effects can be seen on the skin.
A general darkening of the skin (melanosis) is the most common symptom
- often observed on the palms. Dark spots on the chest, back, limbs, or
gums have also been reported. Oedema (swelling of hands and feet) is often
seen. A more serious symptom is keratosis, or hardening of skin into nodules,
often on palms and soles. This consists of an overgrowth of the Kasatin
skin-structure with the development of numerous warts, ridges on the finger-nails
and coarseness of the hair.
WHO estimates that a period of five to ten years exposure to arsenic
is needed to reach this stage.
The only treatment is to find the source of poisoning and to stop
people from drinking the contaminated water.
Once past this stage, complications set in as clinical symptoms become
more pronounced and the internal organs are affected. Enlargement of liver,
kidneys, and spleen have been reported. Some research indicates that conjunctivitis
(pinkeye), bronchitis and diabetes may be linked at this stage, to arsenic
exposure. Symptoms may also indicate an inflammation of the peripheral
nerves and if the condition is allowed to persist, palsies may set in and
the patient becomes apathetic. The final stage is malignancy - when tumours
or cancers (carcinoma) affect the skin or other organs. At this time affected
persons may develop gangrene or skin, lung, or bladder cancer.
The United States Environmental Protection Authority (USEPA) estimates
that the risk of developing skin cancer from a lifetime of drinking contaminated
water is 5 in 100,000 per mgm/L arsenic. The required exposure times are
not well understood, and doubtless depend on concentration, but WHO estimates
that carcinoma can develop after ten to twenty years of exposure. If exposure
in Bangladesh began fifteen years ago it may still be too early to detect
an increase in mortality from cancer.
Examination of the liver-tissue of arsenic patients has disclosed a
severe deficiency in selenium which is able to prevent the effects of the
arsenic. Selenium in the diet is therefore essential for combatting exposure
but this can be found only in eggs, milk and a few other foodstuffs that
are all beyond the purchasing capcity of the poor.
In the light of recent epidemiological evidence linking arsenic and
cancers, WHO in 1993 decreased its recommended maximum value for arsenic
in drinking water from 0.05 to 0.01 mg/l. The USEPA and EC are considering
revising their limits, currently at 0.05 mg/l. All of the standards are
based on total arsenic content, regardless of speciation.
Although various treatment methods have been adopted to remove the arsenic
from drinking water under laboratory and field conditions, the major mode
is by physical-chemical treatment methods. Various treatment methods include:
- adsorption-co-precipitation using iron and aluminium salts
- adsorption on activated alumina/activated carbon/activated bauxite
- reverse osmosis
- ion exchange
- oxidation followed by filtration.
The United States Environmental Protection Agency (USEPA) have summarised
coagulation with iron and aluminium salts and lime softening as the most
effective treatment process for removing arsenic from water to meet the
interim primary drinking water regulations standard of 0.05 mg/L .
In the case of Bangladesh, inorganic arsenic in huge quanities (in thousand
of tons) has been released into the groundwater. Tests in West Bengal revealed
that one single tube well released 150 kg of arsenic/ year. If no safe
remedial measures are quickly forthcoming, the only option is to return
immediately to the use of surface water for drinking, bathing and irrigation.
But as water collected from the rivers; ponds; lakes; canals; haors; etc.
is polluted and must be purified by boiling or by the use of chemicals
like aluminium sulphate or ferrous salts, finding a technology that will
be simple and easy for people to use at a cost low enough is imperative.
One such technology is solar radiation. This is a simple and effective
method that can be applied to combat water-borne and water related diseases
that are prevalent in Bangladesh. Dr. O. Odeyemi, a visiting UNU Fellow
at the Brace Research Institute in Quebec, Canada has focused mainly on
the design and adaptation of systems that can be used and maintained by
the 1.4 billion inhabitants of rural areas of the world. The process is
so simple and it could be the immediate answer to the incidence of preventable
water-borne and water related diseases - and it is attractive because it
is a virtually costless way to render contaminated water fit for human
The technique involves exposing transparent glass or plastic bottles
of water obtained from nearby streams and other sources, for a period of
2 to 4 hours to full sunlight. It has been noticed that under these conditions,
harmful pathogenic organisms that may be present in the water are killed,
provided the initial degree of water contamination is not excessive. Recent
reports from Canada say they have had great success with transparent plastic
bags filled with water.
As researchers have successfully demonstrated that sunlight will destroy
much of the faecal bacteria present in contaminated drinking water - but
the process is especially effective if the water contains a sufficient
amount of oxygen. An easy way to ensure this is to oxygenate the water
before hand by mixing it with air.
As solar photo-disinfection can be carried out in the home by individuals,
families or small communities without any need for a significant financial
investment or external agency support - (the only requirement being a sufficient
number of bottles or clear plastic bags to provide enough drinking water
to meet each person's daily needs) - solar water treatment might be the
answer to the problem of arsenic-contamination for a low- income community
like ours where the cost of engineering solutions may prove prohibitive.
An alternative technology that may be cost-effective is Ultra-violet
Disinfection which uses an ultraviolet (UV) light source enclosed in a
transparent protective sleeve. This is mounted in such a manner that the
water that passes through the flow chamber admit the UV rays and absorb
them into the stream. These rays are able to destroy bacteria and inactivate
many viruses. This kind of system disinfects the water without the need
for adding chemicals and as a result, possesses some of the benefits of
distillation. It neither creates new chemical complexes nor changes the
taste or odor of the water - and - it does not remove any beneficial minerals
that may be in the water. Ultraviolet light safely and reliably disables
the DNA of bacteria and viruses in local water supplies, destroying their
ability to reproduce and rendering them harmless. It consists of a germicidal
ultraviolet (UV) lamp positioned above a shallow water pan. Water flows
through the unit by gravity, staying in the disinfection chamber for 12
seconds to ensure adequate disinfection. However if the water is partially
treated by the sediment process and carbon filter prior to passing through
the UV flow chamber, it is more effective.
UV Waterworks is one such system worth considering as an answer to the
problem of arsenic-contamination in Bangladesh. UV Waterworks has a maximum
flow rate of 15 liters (4 gallons) per minute. The electronic components
are based on standard, off- the-shelf, mature technologies. The basic unit
(Model UVW2.3NC) consumes 40 watts of electricity and accommodates 120
and 220 V AC or 12 V DC. The cost to operate UV Waterworks is approximately
four cents per tonne of water.
Since UV Waterworks relies on gravity for water flow, it can be used
with any water source. The only electricity needed is for the UV lamp,
which means that it can be powered by a car battery, a bicycle pump generator,
grid electricity or solar, wind or hydro power. (Solar, wind and micro-hydro
power packages are available through the manufacturer World Health Incorporated).
One unit feeding into an enclosed water storage tank can easily provide
sufficient water for one household for all water uses or for a village
of up to 1,500 people if water is used primarily for drinking and cooking.
(In fact, one unit feeding water into a 5,000-10,000-gallon storage tank
can serve approximately 150 homes in the United States, the highest water-use
country in the world.) The size of the water storage tank needed depends
on the volume of water needed during peak use hours in any one household
or among all water users connected to the tank.